Microwave communication systems commonly consist of an Outdoor Unit (ODU) connected to a microwave antenna. The microwave antenna is pointed at another microwave antenna with another ODU connected to it. The pair of ODUs and associated antennas comprise a link. The ODU typically contains a transmitter and a receiver to transmit and receive data to and from another ODU through the antennas, the client's network.
Commonly, two ODUs are connected to a single antenna through a hybrid coupler. The hybrid coupler adds significant loss to the transmit and receive signals of the ODU, reducing the system gain. This loss is undesirable since the system gain determines the distance that can be spanned between antennas in a link. A greater loss translates to increased cost in purchasing and maintaining a greater number of antennas in a linked network. Another limitation of the hybrid coupler is that only two ODUs can be connected to it. If one ODU fails in such a system, the effect on network traffic can be substantial. In addition, the limited isolation between ODUs through the hybrid coupler can cause interference.